This invention relates in general to hydrostatic level apparatus and, more specifically, such apparatus adapted for measuring existing vertical elevation and for setting relative differential elevations.
A wide variety of instruments exist for measuring relative levels and setting uniform or differential levels at spaced locations over large areas, in many cases where a clear line of sight does not exist between the different locations.
Typically, levels and differences in elevation are checked and determined using transits sighted to a leveling rod or rotating laser light sources which create a line of light on objects in the plane of rotation. These instruments generally require care and skill in setting up, often require two operators and cannot be used where there is not a continuous line of sight between locations to be leveled, as in the case of different rooms in a building, etc., and often cannot be used in very tight quarters.
To overcome these problems, systems, often called "water leveling systems", have been developed which operate under the principal that a liquid, such as water, in a U-shaped tube will always seek the same level in both legs. Such devices range from very simple applications utilizing a transparent hose filled with water, with two persons holding the ends at the same level, to very complex systems including means for filling and emptying the system, optical means for precise measurements, etc. In general, these systems have problems in requiring two persons to set up and operate them, lack of easy portability, a tendency to spill the liquid during use, and a lack of versatility, e.g., the ability to measure great differences in elevation, the ability to measure elevation of both floors and ceilings, etc. Many such systems include a supplementary tank to supply liquid to the system. These tanks cause errors in measurement unless carefully calibrated during use. Also, prior systems generally are difficult to use for leveling low-lying structures, such as the underside of mobile homes and the like.
Among the prior art water levels are those described by Izumitani in U.S. Pat. No. 5,267,782, Fields in U.S. Pat. No. 4,691,445 and Hoffmeyer in U.S. Pat. No. 5,309,645. While each of these is useful for a specialized purpose, using complex mounting and level reading means, they are not versatile and useful for varied leveling purposes.
Thus, despite the large number of known water leveling systems, there is a continuing need for such systems having improved portability, the ability to measure levels from near the floor to ceiling height or higher, improved ease of use by one person and having increased versatility.